Angular dependence of the ferromagnetic resonance spectrum in continuous/heterogeneous multilayers

J. GÓMEZ; J. L. WESTON; A. BUTERA

Rio de Janeiro, Brazil

Workshop; VIII LAW3M; 2007

We have analyzed the magnetic behavior of a trilayer formed by two continuous ferromagnetic layers, Fe and permalloy (Ni80Fe20), separated by a granular film of Fe- SiO2. The study of the Fe/Fe-SiO2/Ni80Fe20 trilayer was made as a function of the Fe volume concentration x (0.45 < x < 0.85), and the spacer thickness t (t = 1, 2, 4, 9 and 18 nm) of the granular layer. Granular films were prepared using rf sputtering from a mosaic target. Continuous ferromagnetic layers of fixed thickness were made using magnetron dc sputtering. Room temperature ferromagnetic resonance (FMR) measurements made at Q-band (n = 34 GHz) show two absorption modes, one at low fields and another at higher fields. Starting from the Smit and Beljers formalism, we have developed an adapted model to describe the FMR spectra that are observed in this kind of systems. The model allowed us to study the influence that different parameters (e.g. the Fe concentration and the thickness of the granular layer) have on the overall lineshape of the spectra. The dependence of the low field mode with x and t indicates that the granular layer strongly interacts with the Fe layer whereas the permalloy layer is almost uncoupled with the rest of the layers. Dc magnetization measurements confirm this assumption.